/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.server;

import java.util.Collections;
import java.util.Map;

import org.springframework.core.NestedExceptionUtils;
import org.springframework.core.NestedRuntimeException;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Base class for exceptions associated with specific HTTP response status codes.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 5.0
 */
@SuppressWarnings("serial")
public class ResponseStatusException extends NestedRuntimeException {

    private final int status;

    @Nullable
    private final String reason;


    /**
     * Constructor with a response status.
     *
     * @param status the HTTP status (required)
     */
    public ResponseStatusException(HttpStatus status) {
        this(status, null, null);
    }

    /**
     * Constructor with a response status and a reason to add to the exception
     * message as explanation.
     *
     * @param status the HTTP status (required)
     * @param reason the associated reason (optional)
     */
    public ResponseStatusException(HttpStatus status, @Nullable String reason) {
        this(status, reason, null);
    }

    /**
     * Constructor with a response status and a reason to add to the exception
     * message as explanation, as well as a nested exception.
     *
     * @param status the HTTP status (required)
     * @param reason the associated reason (optional)
     * @param cause  a nested exception (optional)
     */
    public ResponseStatusException(HttpStatus status, @Nullable String reason, @Nullable Throwable cause) {
        super(null, cause);
        Assert.notNull(status, "HttpStatus is required");
        this.status = status.value();
        this.reason = reason;
    }

    /**
     * Constructor with a response status and a reason to add to the exception
     * message as explanation, as well as a nested exception.
     *
     * @param rawStatusCode the HTTP status code value
     * @param reason        the associated reason (optional)
     * @param cause         a nested exception (optional)
     * @since 5.3
     */
    public ResponseStatusException(int rawStatusCode, @Nullable String reason, @Nullable Throwable cause) {
        super(null, cause);
        this.status = rawStatusCode;
        this.reason = reason;
    }


    /**
     * Return the HTTP status associated with this exception.
     *
     * @throws IllegalArgumentException in case of an unknown HTTP status code
     * @see HttpStatus#valueOf(int)
     * @since #getRawStatusCode()
     */
    public HttpStatus getStatus() {
        return HttpStatus.valueOf(this.status);
    }

    /**
     * Return the HTTP status code (potentially non-standard and not resolvable
     * through the {@link HttpStatus} enum) as an integer.
     *
     * @return the HTTP status as an integer value
     * @see #getStatus()
     * @see HttpStatus#resolve(int)
     * @since 5.3
     */
    public int getRawStatusCode() {
        return this.status;
    }

    /**
     * Return headers associated with the exception that should be added to the
     * error response, e.g. "Allow", "Accept", etc.
     * <p>The default implementation in this class returns an empty map.
     *
     * @since 5.1.11
     * @deprecated as of 5.1.13 in favor of {@link #getResponseHeaders()}
     */
    @Deprecated
    public Map<String, String> getHeaders() {
        return Collections.emptyMap();
    }

    /**
     * Return headers associated with the exception that should be added to the
     * error response, e.g. "Allow", "Accept", etc.
     * <p>The default implementation in this class returns empty headers.
     *
     * @since 5.1.13
     */
    public HttpHeaders getResponseHeaders() {
        Map<String, String> headers = getHeaders();
        if (headers.isEmpty()) {
            return HttpHeaders.EMPTY;
        }
        HttpHeaders result = new HttpHeaders();
        getHeaders().forEach(result::add);
        return result;
    }

    /**
     * The reason explaining the exception (potentially {@code null} or empty).
     */
    @Nullable
    public String getReason() {
        return this.reason;
    }


    @Override
    public String getMessage() {
        HttpStatus code = HttpStatus.resolve(this.status);
        String msg = (code != null ? code : this.status) + (this.reason != null ? " \"" + this.reason + "\"" : "");
        return NestedExceptionUtils.buildMessage(msg, getCause());
    }

}
